The present invention relates to a portable radio apparatus, and more particularly to a portable radio communication apparatus for supplying a plurality of circuits including a large current consuming circuit with optimal power for the operation of each from a plurality of types of batteries.
A conventional radio apparatus has a main unit and a pack of chargeable batteries, which serves as power source for the main unit. The main unit has a power amplifier for supplying high frequency power to a whip antenna and a transmit/receive signal processing section for processing transmit signals and receive signals. The battery pack has built-in nickel cadmium (Ni-Cd) batteries or nickel metal hydride (Ni-MH) batteries.
The main unit and the battery pack have a detaching mechanism, which allows them to be detached when the batteries are to be charged and to be put together again when the charging is completed. The main unit and the battery pack respectively have power input terminals and power output terminals, which come into contact with each other when the two units are joined. In such a portable radio apparatus, when the operating voltage is to be supplied to the power amplifier and the transmit/receive signal processing section of the main unit, the circuit operation may be adversely affected by any voltage fluctuation. For instance, if the voltage of the Ni-Cd batteries has fallen to a certain prescribed low level, the transmit/receive signal processing section will still operate normally, but the power amplifier may not, failing to supply the required transmitting power. Or, when the power amplifier does operate, i.e. at the time of transmission, if a large current will flow to invite a substantial voltage drop, the transmit/receive signal processing section may be prevented from normal operation. For this reason, batteries of a relatively high-voltage, which is needed to obtain transmitting power efficiently, are used, and at the same time there is provided a stabilizing circuit for converting this high voltage to a low voltage required for the operation of the transmit/receive signal processing section. Furthermore, where the circuitry of the apparatus is complex, a large number of stabilizing circuits are needed to supply a stabilized voltage to each processing circuit.
Another known such apparatus according to the prior art is described in the Gazette of the Patent Laid-open No. 2322222 of 1987. The apparatus disclosed in this gazette is provided with a control unit for the transmission output for detecting the source voltage that is supplied and sending out the optimal transmission power on the basis of the voltage. However, this transmission output control unit, like the conventional circuit first mentioned, also involves the problem of complex circuitry.